Sulfoureido Lipopeptides from the Marine Sponge <i>Discodermia kiiensis</i>

New <i>N</i>-sulfoureidylated lipopeptides, sulfolipodiscamides A–C (<b>1</b>–<b>3</b>), were isolated by gel filtration chromatography of the <i>n</i>-butanol fraction of the marine sponge <i>Discodermia kiiensis</i>. By extensive NMR analyses and high-resolution mass spectrometry, the structures of <b>1</b>–<b>3</b> were elucidated as having an unprecedented <i>N</i>-sulfoureidyl group on the d-citrulline residue, a distinct feature that was not found in the structurally related lipodiscamides A–C (<b>4</b>–<b>6</b>), derived from the ether fraction of the same sponge. Furthermore, the absolute configurations of <b>1</b>–<b>3</b> were confirmed by comparisons of the HPLC retention times of the hydrolytic products and the corresponding authentic lipodiscamides. Interestingly, sulfolipodiscamide A displayed a 2.3-fold increase in cytotoxicity against murine leukemia (P388) cells, compared to the unconjugated parent compound

Spiro-Ring Formation is Catalyzed by a Multifunctional Dioxygenase in Austinol Biosynthesis

Austinol, a fungal meroterpenoid derived from 3,5-dimethylorsellinic acid, has a unique chemical structure with a remarkable spiro-lactone ring system. Despite the recent identification of its biosynthetic gene cluster and targeted gene-deletion experiments, the process for the conversion of protoaustinoid A (<b>2</b>), the first tetracyclic biosynthetic intermediate, to the spiro-lactone preaustinoid A3 (<b>7</b>) has remained enigmatic. Here we report the mechanistic details of the enzyme-catalyzed, stereospecific spiro-lactone ring-forming reaction, which is catalyzed by a non-heme iron-dependent dioxygenase, AusE, along with two flavin monooxygenases, the 5′-hydroxylase AusB and the Baeyer–Villiger monooxygenase AusC. Remarkably, AusE is a multifunctional dioxygenase that is responsible for the iterative oxidation steps, including the oxidative spiro-ring-forming reaction, to produce the austinol scaffold

Molecular Basis for Stellatic Acid Biosynthesis: A Genome Mining Approach for Discovery of Sesterterpene Synthases

The search for a new sesterterpene synthase in the genome of <i>Emericella variecolor</i>, which reportedly produces diverse sesterterpenoids, is described. One gene product (a chimeric protein with prenyltransferase and terpene cyclase domains) led to the synthesis of a novel tricyclic sesterterpene, stellata-2,6,19-triene (<b>1</b>), from DMAPP and IPP, and the hydrocarbon was further transformed into stellatic acid (<b>2</b>) by cytochrome P450 monooxygenase encoded by the gene adjacent to the sesterterpene synthase gene

Chojalactones A–C, Cytotoxic Butanolides Isolated from <i>Streptomyces</i> sp. Cultivated with Mycolic Acid Containing Bacterium

The soil-derived bacterium, <i>Streptomyces</i> sp. CJ-5, was cocultured with the mycolic acid-containing bacterium <i>Tsukamurella pulmonis</i> TP-B0596. The combined culture method significantly enhanced the production of the secondary metabolites in <i>Streptomyces</i> sp. CJ-5, leading to the isolation of three novel butanolide chojalactones A–C (<b>1</b>–<b>3</b>), with unusual γ-butyrolactone scaffolds. The complete structures, including the absolute configurations of <b>1</b>–<b>3</b>, were determined based on spectroscopic data and total syntheses. In methylthiazole tetrazolium (MTT) assays, <b>1</b> and <b>2</b> showed moderate cytotoxicity against P388 cells

The biosynthetic gene cluster and proposed biosynthetic pathway to kasumigamide.

<p><b>(a)</b> ORFs encoded in the putative kasumigamide biosynthetic gene cluster, <i>kasA-I</i>. Double-headed arrows show the location of pDCYN1-2. The ORFs related to PKS-NRPS are highlighted in red. Putative transposases are colored in green. <b>(b)</b> The domain organization and proposed biosynthetic pathway to kasumigamide.</p

Complete Biosynthetic Pathway of Anditomin: Nature’s Sophisticated Synthetic Route to a Complex Fungal Meroterpenoid

Anditomin and its precursors, andilesins, are fungal meroterpenoids isolated from <i>Aspergillus variecolor</i> and have unique, highly oxygenated chemical structures with a complex bridged-ring system. Previous isotope-feeding studies revealed their origins as 3,5-dimethylorsellinic acid and farnesyl pyrophosphate and suggested the possible involvement of a Diels–Alder reaction to afford the congested bicyclo[2.2.2]­octane core structure of andilesins. Here we report the first identification of the biosynthetic gene cluster of anditomin and the determination of the complete biosynthetic pathway by characterizing the functions of 12 dedicated enzymes. The anditomin pathway actually does not employ a Diels–Alder reaction, but involves the nonheme iron-dependent dioxygenase AndA to synthesize the bridged-ring by an unprecedented skeletal reconstruction. Another dioxygenase, AndF, is also responsible for the structural complexification, generating the end product anditomin by an oxidative rearrangement

Comparative analysis of domain organizations of the putative kasumigamide biosynthetic gene clusters.

<p>Each gene cluster derived from <b>(a)</b> <i>D</i>. <i>acidovorans</i> CCUG 274B <b>(b)</b> <i>Herbaspirillum</i> sp. CF444 <b>(c)</b> ‘Entotheonella’ sp. <b>(d)</b> <i>M</i>. <i>aeruginosa</i> NIES-87.</p

Cytochrome P450 for Citreohybridonol Synthesis: Oxidative Derivatization of the Andrastin Scaffold

A biosynthetic gene cluster similar to that for andrastin A (<b>1</b>) was discovered in Emericella variecolor NBRC 32302. Ctr-P450, a cytochrome P450 uniquely present in the cluster, was coexpressed with the andrastin A biosynthetic genes, leading to the production of the antifeedant agent citreohybridonol (<b>4</b>), along with four new andrastin derivatives. The results revealed the unusual multifunctionality of Ctr-P450 and indicated that this approach can be applied for further natural product diversification

Substrate selectivity of A domains.

<p>The relative adenylation activity was estimated by the malachite green phosphate assay. Error bars represent SEM (n = 3).</p

Symbiont bacteria bearing <i>kas</i> genes.

<p><b>(a)</b> Phase contrast image of <i>D</i>. <i>calyx</i> homogenate. A filamentous bacterium ‘Entotheonella’ sp. is designated as “F”. A small filamentous bacterium with bright color is designated as “S”. Scale bars was 20 μm. <b>(b)</b> PCR analysis of dissected cells with the <i>kas</i>-specific primers pair, DCKS10F/DCKS10R (<b><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0164468#pone.0164468.s015" target="_blank">S1 Table</a></b>), using dissected cells (“F” or “S”) as templates.</p